The effect of a diet supplemented with yogurt containing live lactobacilli (LAB) - Lactobacillus bulgaricus and Streptococcus thermophilus - on the response of inbred mice to infection with Salmonella typhimurium was elaborated. The results of our experiments were consistent with the hypothesis that modifications of the microflora influence the adherence of S. typhimurium to intestinal mucosa, the natural antibacterial activity of the Peyer's patches lymphocytes, the accumulation of the macrophages in the liver, the proliferative responses of the splenocytes. The relationship between modifications of the immune response following ingestion of yogurt with live LAB and increased defense mechanisms was confirmed by the bacterial counts in livers and spleens and by the reduced mortality to S. typhimurium infection.

Several new quinolone derivatives were investigated for their influence on human lymphocyte blastogenesis and gamma-interferon production following concanavalin A stimulation. All the antimicrobials induced inhibition of lymphocyte DNA synthesis. The gamma-interferon measurements showed that nalidixic acid and norfloxacin have a negative influence on lymphokine production and release.

A time-dependent degree of immunosuppression or immunostimulation which may be correlated to pharmacokinetic variables was obtained by administering a single dose of ofloxacin, norfloxacin, pipemidic and piromidic acid to healthy volunteers. The plasma samples collected before drug administration and then at various time intervals were tested for their immunomodifying activity by employing a modified 2-way mixed lymphocyte reaction and a PMN chemotactic assay. Our results show that some of the quinolones tested--norfloxacin, pipemidic acid, piromidic acid--have an immunosuppressive activity.

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